Humans and Light - The Importance of Light and the Effects of Light on People

Lumen is the Latin word for light. Element is that which is essential. So today I am going to visit with you about light that is essential for your health, well-being, and sleep.

Who am I? I was a hospice volunteer for several years and have been the owner, with my husband, of a commercial lighting company since 2008. I’m a member of the National Association of Independent Lighting Distributors, I am certified as a Lighting Specialist, I hold the Aging in Place Executive Certificate in Home Modification through the USC Leonard Davis School of Gerontology, and I am an Invited Member of the Humancentric Lighting Society which is an international society of lighting researchers, experts and neuro-scientists. I have also been the co-chair of the Walk to End Alzheimer’s for 2018-19.

I became interested in lighting based on having relatives who suffered with dementia, seeing what was happening in the lighting industry today, and wondering if lighting could have made a difference for them as they lived with that disease.

What is light?


Light is energy. Light gives energy to plants to grow. When we compare how we feel on a bright, blue, sunny day to how we feel on a gray and cloudy day it is easy to see and understand the energy we get from light, and that light is energy. Natural light is the light outside. It is dynamic and constantly changing throughout the day. Clouds go across the sun. The light changes with the seasons. In contrast, electrical light is the very same light all the time, 24 hours a day. It is static. It may be possible to dim or brighten the intensity with controls, but our bodies will always read electrical light the same way. Up until about 120 years ago, our ancestors lived under that constantly changing light that is present outside. They spent 90% of the day outside. Now, we spend 90% of our days inside under static electric light. I believe many of the health problems we are living with today can be attributed to that.

mal illumination is a lack of good light.jpg


Means lack of good light. This is similar in concept to malnutrition. We can be surrounded by food, but if we are making the wrong choices, we will still suffer from malnutrition. In the same way, we can be surrounded by light twenty-four hours a day, but if it is not the light that we biologically need at the correct time, we will suffer from mal-illumination and see the consequences in our health.

Our eyes: We have cones and rods in our eyes which help us to see color and shape in dim light. In 2002, researchers discovered IPRGC: Intrinsically Photo-Sensitive Retinal Ganglion Cells. They had known for about 80 years prior to this discovery that there was something else that our eyes were detecting.  In 2002 researchers in both the US and Europe, on the same day, announced the discovery of these cells. There is a visual component to what these cells do, but most of what they do is non-visual. These cells are photo-sensitive not only to the amount of light, but also to the color of light. They send a message through a different nervous system, down the spinal column and into the pineal gland. This is what sets our circadian rhythm.  Researchers now know that there are even more ganglion cells, and their functions have not yet been identified. But we do know that just as the cells in our ears function for both hearing and balance, the cells in our retinas are used for more than just sight. They are responsible for setting our circadian rhythm. 


Light and circadian rhythm:

Circa means about, and dia means day. So, circadian rhythm is the rhythm that repeats in about a day. Our world runs on a 24-hour cycle. However, as humans, our natural circadian rhythm is about 5-7 minutes longer than that. How many of you have ever been jet-lagged? When we are jet-lagged we are more prone to illness, accidents, falls, and poor decision-making. Can you imagine being perpetually jet-lagged and adding five to seven minutes every day? Just think how far off we would be in the course of a week, a month, or a year. This is how we can feel when our circadian rhythm is continually disrupted. Our circadian rhythm is responsible for the proper function of our hormones, heart rate, and body temperature. It is present in humans, animals, and plants. This rhythm is generated by our internal timeclock, the pineal gland that synchronizes to light and dark cycles. It is also what accounts for our waking up at the same time every day, and entrainment.

Entrainment is what happens first thing in the morning when light hits the cells in our retina.

It sets us to our 24-hour day.  This is entrainment, and it is why light is so very, very important in the morning. A healthy circadian rhythm gives us restorative sleep, lowered stress, less anxiety and depression, lower risk for cardiovascular disease and type two diabetes, lower incidence of breast and prostate cancer, and lower incidence of hormonal cancers.  Since circadian rhythm is responsible for the release of hormones, it makes sense that diseases that are the result of hormonal imbalances could potentially be caused by disrupted circadian rhythm caused by improper light. Studies have shown that nurses who work night shifts have a higher incidence of breast cancer. Researchers are finding that working under artificial light at night, not getting proper sleep, and not having a set circadian rhythm can increase the incidence of disease.

How can we have a healthy circadian rhythm?

First thing in the morning and into the early afternoon we should be exposed to bright blue light. Blue light suppresses the hormone melatonin. When we don’t have melatonin working, we have serotonin and cortisol working instead. These are our feel-good, energy, “get-going” hormones. These are what we want in the early and middle part of day. Take walks outside on lunches and breaks to get exposure to the blue light. I recommend getting outside, but we do now have humancentric lighting technology that can provide that dynamic and blue light indoors also. Both light and darkness are required for a healthy circadian rhythm. We need total darkness for good, restorative sleep. If you hold  your arm out in front of you and can still see your hand, there is too much light in the room for deep, restorative sleep to take place.

What is Humancentric Lighting and why is it important?

Humancentric lighting is lighting that is aimed at providing the right lighting for activities at the right place and time. Our ancestors lived mostly under that beautiful, outdoor, dynamic light. With the development of humancentric lighting, we can now bring that dynamic and blue light inside to our workplace and home.

The Aging Eye:

Eyes - the iris fades and weakens with age.jpg

The iris (the colored part of eye) fades as we age. The iris is also a muscle, and it controls pupil constriction and dilation. As the iris fades and weakens with age, the pupil is not dilated and constricted optimally and does not respond as well to light. Age also causes the lens of the eye to yellow and become cloudy. Think about setting a newspaper in the sun and seeing that it yellows with time. This is similar to what happens to the lens in the aging eye. These are common, normal changes to the aging eye. As a result of these changes to our eyes, we need more light to read and do tasks. Studies show that a 50-year-old needs 10 times as much light as a 10-year-old to read. A 65-year-old needs 15 times as much light as a 10-year-old to read, and a person with a vision impairment will likely need three to four times as much light as a person of the same age with no vision impairment. Dementia and diabetic retinopathy are examples of conditions that can cause vision impairments. So, if you are 65 years old and have a visual impairment in addition to a normally aging eye, you could potentially need 45 to 60 times as much light as a 10-year-old to do the same task.

My passion for light and health - especially as we age:

light and health are related- especially as we age

Much of my passion for, and interest in, light came from wanting to see how light could impact those living with dementia. A new realm of scientific studies is showing that many of the problems that affect dementia patients such as sundowning, caloric restriction due to lack of appetite, agitation, depression, and not sleeping well can be improved with exposure to blue light during the day. How many of you feel really good when you don’t get good sleep? Research has shown a reduction in agitation, falls, and depression when people are exposed to blue light at the proper time of the day, allowing them to get a better night’s sleep. Studies have shown that people in nursing facilities, if they do not have the mobility to go outside on their own, are generally only exposed to 10 minutes of blue light a day. Knowing that we need blue light for sleep and circadian rhythm, imagine being stuck inside almost 100% of the day under static, artificial light that can have such a detrimental impact on your health.

Example of circadian lighting installed at local memory care facility:

We installed under-bed lighting so residents could be checked at night without having to be disrupted by overhead lights. We installed overhead humancentric lamps that provide a very rich, blue light between the hours of 10:00am and 2:00pm. In the evening, starting at about 4:00pm, the lamps begin to change in intensity and color, eliminating the blue light and signaling the body to increase melatonin. I was with my staff for the full day of this installation, which we had prepared for and worked toward for a year. When residents were brought back into the space after the lights had been installed, three of the residents immediately said, “I feel like I’m outside”.  It was an emotional moment because it showed that there was a tangible difference, and that the residents felt better. They didn’t know why, but they knew that they felt better. We are currently in the process of upgrading four more of the houses in that facility.

Benefits of humancentric lighting:

The benefits of humancentric lighting are an entrained and healthy circadian rhythm, improved mood, and improved visual acuity. There is also a financial incentive to install humancentric lighting because since these lights are LEDs, they use less energy and provide savings on energy and maintenance costs. Studies are showing that when asked, the #1 thing that office workers wished they had was better lighting. Humancentric lighting has also been shown to improve the productivity of employees.

Humancentric lighting and sleep:

human centric lighting and sleep quality

How many of you get eight hours of sleep a night? That is what is recommended for a healthy adult. Ongoing lack of sleep or poor-quality sleep increases the risk of health problems such as diabetes, heart disease, high blood pressure, depression, and obesity. Melatonin and cortisol are hormones with opposite functions. Blue light suppresses melatonin, which is our sleep hormone, so we want to be very mindful of that in the evening when we are getting ready for sleep. We begin producing melatonin a couple of hours before we go to sleep, but this process can be interfered with if we are still being exposed to blue light that stimulates cortisol and serotonin. In the Disney movie, “Inside Out”, the story is about a little girl and how they are trying to store memories. Her memories are like bowling balls. This is very true of how our brains work. When we are in our deepest phase of sleep, we store long-term memories. It is also during this deep phase of sleep that our brain is the most active and is cleaning out the amyloid plaques that contribute to dementia and Alzheimer’s disease! I recently learned that during the day, our blood/brain barrier is more closed. Our brain is actually swollen from taking in information. At night, during our deepest phase of sleep, our brain shrinks a little bit which makes it possible for the cleaning process to take place.   If we are not getting good, deep sleep, this important process is not happening. In talking to staff in memory care facilities, I have found that they understand just how important it is to do everything possible to help residents to be able to store memory.

Getting a good night’s sleep: Exposure to blue light too close to bedtime can delay deep sleep for up to 90 minutes. We need good exposure to blue light between 10:00am and 2:00pm, and elimination of blue light as we move closer to bedtime. I wear special glasses with yellow lenses that block blue light starting a couple of hours before bed. All these things can prepare your body and brain for sleep and improve your sleep quality. Eliminate exposure to sources of blue light created by alarm clocks, TV, Smartphones, Ipads, E-readers, and night lights. Also, make sure that you sleep in total darkness.

Example of lighting’s effect on sleep:

I worked with a gentleman that had been diagnosed with circadian disruption. He had been on medication and was still having a difficult time navigating his day because of fatigue. With my Aging in Place certificate, I have developed a screening program for evaluating the lighting in homes. I went in and changed the lighting he was using in the morning and evening, and almost immediately he was able to see an improvement in his sleep and his ability to get up in the mornings and function better throughout his day.

Benefits of a good night’s sleep: Improved wound healing, improved mood, decreased risk of falls, better balance, increased cognitive function, better reaction time, hormones function better. Is there anything in this list that you are not interested in?